This application is the national phase under 35 U.S.C. xc2xa7371 of PCT International Application No. PCT/SE99/00107 which has an International filing date of Jan. 27, 1999, which designated the United States of America.
The present invention relates to an operating device for anti-skid devices.
Automatically operating anti-skid devices generally comprise an operating unit and an operating arm pivotally carried by said unit. An anti-skid means, usually a roller, to the periphery of which is attached a number of anti-skid elements in the form of short pieces of chain, is rotationally mounted on the operating arm. By pivoting the operating arm the anti-skid means may be shifted between an active position, in which the roller abuts against the side face of a vehicle wheel so as to be rotated thereby and to throw pieces of chain in between the wheel and a support, and a position of rest, wherein the roller is spaced from the wheel and lifted to a position underneath the vehicle.
When anti-skid devices of this kind are used it is important that the rotary anti-skid means abuts against the vehicle wheel at exactly the right place. It has also been found that the angle of the rotating anti-skid means in contact with the vehicle wheel relative to the plane of rotation of the vehicle wheel determines the degree of anti-skid effect that it is possible to obtain.
In the position of rest of the anti-skid device, the rotary anti-skid means must be shifted to a suitable location underneath the vehicle and spaced from the road surface as well as from the vehicle wheel.
Anti-skid devices of the kind to which the present invention relates generally are mounted on the rear axle of heavy-duty vehicles. In heavy-duty vehicles, considerable differences of appearance exist as to the configuration and design of the mounting place and the rear-axle area. Furthermore, the tolerances as to the design and the position of the rear axle are considerable in this type of vehicle. Consequently, it becomes necessary to mount the anti-skid device in a different manner in each vehicle model. For each discrete mounting instance the anti-skid device also needs to be set individually in order for the rotary anti-skid means to be correctly located in the active as well as in the passive position.
Particular difficulties are experienced in anti-skid devices that are to be mounted on buses and smaller vehicles because of the extremely reduced space available. This problem is felt to an increasing extent also in heavy-duty vehicles, since in modern trucks the available space around the rear axle tends to become increasingly smaller. Consequently, high demands are placed on anti-skid devices to be as small as possible.
EP-A-162 823 describes an anti-skid device of the kind defined above, wherein the operating unit comprises an air cylinder which is remote-connected to the operating arm via a lever and a first wire in order to pivot said arm to the active position by transmission of traction via the wire. A return spring is connected to a second wire, which in turn is connected to the operating arm in order to bias the spring, when the arm assumes the active position. Return of the operating arm to the position of rest deactivates the air cylinder, whereupon the return spring resets the operating arm to the position of rest by transmission of traction via the second wire.
A wire construction of this nature is sensitive to the salty and moist environment prevailing wintertime in the area of the vehicle chassis. In constructions of this kind, problems frequently arise from corrosive attacks on the wires, making them stick or rust away. In addition, stretching of the wires due to tensile stress is a possibility that also must be taken into consideration.
EP-B-278 896 describes an operating unit for anti-skid devices comprising a drive means in the form of an axially movable rack in engagement with a pinion, the latter in turn connected to the operating arm in order to pivot the latter. The pinion is arranged centrally relative to the area of movement of the rack and is located on the same shaft as the operating arm, for which reason also the operating arm is arranged centrally relative to the area of movement of the rack. Similar constructions are described also in EP-A-487 297 and EP-A-443 455.
A problem encountered in rack/pinion combinations of this kind is that they are complicated and consequently expensive to manufacture and to maintain. Another drawback found in these constructions is that they reduce the space available to the designer in positioning the operating unit underneath a vehicle because of the central location of the operating arm relative to the area of movement of the rack, for which reason it is difficult to position the operating device close to another component underneath the vehicle, which is often necessary.
The object of the present invention is to provide an operating device for anti-skid devices, which is greatly improved over the prior-art solutions described above.
One particular object is to provide an operating unit, which is incorporated in the device and gives the designer considerable freedom in positioning the unit on the bottom face of the vehicle.
These and other objects, which will appear from the following description, have now been achieved according to the teachings of the invention by means of an operating device of the kind defined in the introduction hereto.
Thus, a rotary means, arranged to rotate about a rotational shaft, is connected to a linear drive means, the force of which is exerted in the direction along a longitudinal axis, by means of a string-like drive transmission element in order to translate a linear movement of the drive means into a pivotal movement of an operating arm. The drive transmission element extends essentially along the longitudinal axis of the drive means between the drive means and the rotary means in order to transmit motion in two opposite directions between the drive means and the rotary means.
The drive transmission element is non-rotationally connected to the rotary means, i.e. it is securely attached to the rotary means in the peripheral direction, like, for example, a chain engaging a toothed wheel or a wire tightly lapping a wheel.
In this manner an operating device is provided, wherein the movement of a linear drive means may be translated into a rotational movement of a rotary means without the linear drive means having to extend past the rotary means on two sides of the latter. This makes it possible to install the rotary means in one end area of the operating unit and to connect one end of the operating arm directly to the rotary means, and consequently the operating unit may easily be placed in a convenient position underneath a vehicle, since the operating unit essentially extends in one single direction, from the point of attachment of the operating arm. This direction may be chosen optionally in adaptation to the individual configuration of different vehicles. The opposite end of the operating arm, i.e. the one spaced from the rotary means and the drive transmission element, may support an anti-skid means.
In addition, the operating arm may be pivoted within a large angular range without requiring additional space in more than one direction.
Because the drive transmission between the drive means and the rotary means is produced by a string-like means instead of by direct meshing of teeth on drive means and drive transmission means, respectively, it becomes possible to manufacture the operating unit at a lower cost than hitherto, due to the fact that the drive and rotary means need no longer be formed with a plurality of directly meshing toothed sections that need to be produced to a high degree of precision.
In accordance with a preferred embodiment the drive means act along a longitudinal axis essentially perpendicular to the rotational axis of the rotary means.
In accordance with another preferred embodiment, the drive transmission element is formed with a first portion, which is coupled to the drive means, and with a second portion, which is coupled to the rotary means.
In accordance with yet another preferred embodiment of the invention the drive transmission element extends in a continuous loop around the rotary means and around a deflector means, about which the drive transmission element is arranged to move. In a simple manner, this arrangement enables the drive transmission element to absorb motion in two opposite directions of movement without the element in itself having to be able to absorb compressive forces. Consequently, simple traction-absorbing drive transmission elements may be used, which is economically advantageous.
Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.